Ignition OFF, function

Function requirements for ignition OFF, general points

 Circuit 87M (engine timing ON)

 Circuit 15

Ignition OFF, general points

With ignition OFF, first the engine and then the engine timing are switched off in the CDI control unit (N3/9).

Function sequence for ignition OFF

For ignition OFF the electronic ignition lock control unit (N73) switches off the circuit 15 engine compartment relay (K40/8kG) via the interior CAN (CAN B).

If the CDI control unit receives the "Circuit 15 OFF" signal over circuit 15 engine compartment relay, the following components will be switched off and the processor power-down is started:

– the fuel pump (M3) from FSCU (N118)

– pressure regulating valve (Y74)

– fuel injectors (Y76)

– quantity control valve (Y94)



The AdBlue fluid is suctioned back out of the AdBlue® metering valve (Y129) and the AdBlue metering line in the direction of the AdBlue tank after stopping the engine (after ignition Off) by the extraction pump AdBlue® (A103/2m2). The AdBlue metering line is only partially emptied in the process. The AdBlue® metering valve is opened during the reverse suction process so that no vacuum arises in the AdBlue® pressure line. Since it is not possible to exclude the possibility, after stopping/parking of the vehicle, that the outside temperatures drop into the negative range (for very long stopping/parking times), reverse suction of the AdBlue fluid out of the metering valve and the AdBlue line takes place after each switching off of the ignition

The processor run-on period is determined for the AdBlue® control unit (N118/5) by the CDI control unit and lasts about 4 s. It can, however, last for several minutes due to various functions (such as On-board Diagnosis (OBD), Drive Authorization System (DAs), thermal management).

When computer run-on is complete, the circuit relay 87M (K40/8kN) is switched off and the engine timing system is disconnected from the on-board electrical system (switched off).



System tests are conducted by the CDI control unit during the processor run-on period and the fault memory is updated.

The "circuit 31" ground connection is made from the on-board electrical system battery (G1) via the battery ground point at the front right (W10) and multiple ground lines to the right assembly compartment ground point (for lamp unit) (W2).

When the ignition is OFF, the CDI control unit is supplied with power from the on-board electrical system battery via "circuit 30 fused".